1. Technical Field
The present invention relates to thin film transistors and, particularly, to a carbon nanotube based thin film transistor.
2. Description of Related Art
A typical thin film transistor (TFT) is made of a substrate, a gate electrode, an insulation layer, a drain electrode, a source electrode, and a semiconducting layer. The thin film transistor performs a switching operation by modulating an amount of carriers accumulated in an interface between the insulation layer and the semiconductor layer from an accumulation state to a depletion state, with applied voltage to the gate electrode, to change an amount of the current passing between the drain electrode and the source electrode.
Bipolar TFT has the characteristic of high switching ratio and symmetry, and can be applied in the process of frequency multiplication and frequency mixing. However, because work-function of the material of the source electrode and the drain electrode is not the same as that of the semiconductor layer, a Schottky barrier is created between the semiconductor layer and the source electrode or the drain electrode. Thus, holes or electrons are selectively generated; thereby the symmetry of bipolar TFT is destroyed.
What is needed, therefore, is a TFT that can overcome the above-described shortcomings.